Steering system

ABSTRACT

A steering system includes: an upper bracket that supports a column jacket so that the column jacket is pivotable about a central shaft; a pair of first tooth rows that are supported by the upper bracket and are arranged side by side in an axial direction; and a tooth member that is pivotable together with the column jacket and is movable in a right-and-left direction. The tooth member has second teeth that are formed in two locations spaced apart from each other in the axial direction and that can mesh with the pair of the first tooth rows. The tooth tip angle of first teeth in one first tooth row of the pair of the first tooth rows is different from the tooth tip angle of the first teeth in the other first tooth row that is more distant from the central shaft than the one first tooth row.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2015-137046 filed onJul. 8, 2015 including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a steering system.

2. Description of Related Art

A steering column described in US Patent Application Publication No.2009/0013817 (US 2009/0013817 A1) includes a setting unit, a holdingunit, a tooth plate, a press-on member, and a clamp bolt. The settingunit can be pivoted to adjust the position of the steering column in acertain adjustment direction. The holding unit holds the setting unit.To the setting unit, a jacket unit that holds a steering shaft isattached. The holding unit has a plurality of teeth arranged in theadjustment direction. The tooth plate also has a plurality of teetharranged in the adjustment direction. The clamp bolt is inserted throughthe press-on member and the tooth plate, and can be pivoted togetherwith the setting unit.

By operating a lever attached to the clamp bolt, the press-on member canbe moved toward the holding unit. When the press-on member moves towardthe holding unit, the tooth plate is pressed against the press-on memberto move toward the holding unit. When the teeth of the moving toothplate enter spaces between the teeth of the holding unit, the teeth ofthe holding unit and the teeth of the tooth plate mesh with each other.Thus, the position of the jacket unit in the adjustment direction isfixed.

The adjustment direction defined in US 2009/0013817 A1 is a directionvertically intersecting the axial direction of the steering shaft. Inthe steering column described in US 2009/0013817 A1, the position of thejacket unit in the intersecting direction is fixed by causing the teethto mesh with each other. In this case, meshing strength between theteeth needs to be increased by firmly meshing the teeth with each other,in order to prevent the position of the jacket unit from becomingmisaligned even if a vehicle is subjected to strong impact in acollision.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a steering system inwhich a steering shaft is held by a column jacket and the position ofthe column jacket in a direction intersecting the axial direction of thesteering shaft is fixed by causing teeth to mesh with each other andwhich can increase meshing strength between the teeth.

A steering system according to one aspect of the present inventionincludes: a steering shaft to one end of which a steering member iscoupled; a column jacket that holds the steering shaft and is pivotableabout a pivot axis that is on the opposite side of the steering shaftfrom the one end in an axial direction; a bracket that is fixed to avehicle body and supports the column jacket so that the column jacket ispivotable; an operation member that is operated to allow and preventpivoting of the column jacket with respect to the bracket; a pair oftooth rows each including a plurality of first teeth each of which has atooth trace extending in an orthogonal direction orthogonal to both ofthe axial direction and an intersecting direction verticallyintersecting the axial direction and that are arranged along theintersecting direction, the pair of tooth rows being supported by thebracket and being arranged side by side in the axial direction; and atooth member including a second tooth that has a tooth trace extendingin the orthogonal direction, is formed at least one in each of twolocations spaced apart from each other in the axial direction, and isconfigured to mesh with the pair of tooth rows, the tooth member beingpivotable together with the column jacket and being movable in theorthogonal direction in accordance with operation of the operationmember. In the steering system, a tooth tip angle of the first teeth inone tooth row of the pair of tooth rows is different from a tooth tipangle of the first teeth in the other tooth row that is more distantfrom the pivot axis than the one tooth row.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further features and advantages of the invention willbecome apparent from the following description of example embodimentswith reference to the accompanying drawings, wherein like numerals areused to represent like elements and wherein:

FIG. 1 is a side view of a schematic structure of a steering systemaccording to one embodiment of the present invention;

FIG. 2 is a perspective view of the steering system;

FIG. 3 is a sectional view along line III-III in FIG. 1;

FIG. 4 is an exploded perspective view of a tilt locking mechanism onthe left side;

FIG. 5 is a sectional view along line V-V in FIG. 3;

FIG. 6 is a sectional view along line VI-VI in FIG. 5;

FIG. 7 is a schematic diagram illustrating first tooth rows and secondtooth rows that mesh with each other;

FIG. 8 is a diagram illustrating a released state of the steering system1 in FIG. 6;

FIG. 9 is a diagram illustrating a state in which the second tooth rowsare riding on the first tooth rows in FIG. 5;

FIG. 10 is an exploded perspective view of a tilt locking mechanismaccording to a first modification;

FIG. 11 is an exploded perspective view of a tilt locking mechanismaccording to a second modification; and

FIG. 12 is an exploded perspective view of a tilt locking mechanismaccording to a third modification.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings. FIG. 1 is a side view of aschematic structure of a steering system 1 according to one embodimentof the present invention. In FIG. 1, the left side in the plane of thepage corresponds to the front side of a vehicle body 2 on which thesteering system 1 is mounted, the right side in the plane of the pagecorresponds to the rear side of the vehicle body 2, the upper side inthe plane of the page corresponds to the upper side of the vehicle body2, and the lower side in the plane of the page corresponds to the lowerside of the vehicle body 2.

As seen in FIG. 1, the steering system 1 mainly includes a steeringshaft 3, a column jacket 4, a lower bracket 5, an upper bracket 6, aposition adjustment mechanism 7, a telescopic locking mechanism 8 (seeFIG. 2 described later), and a tilt locking mechanism 9. To one end 3Athat is the rear end of the steering shaft 3, a steering member 11 suchas a steering wheel is coupled. In the steering shaft 3, the other end3B that is the front end thereof is coupled to a pinion shaft 16 of asteering operation mechanism 15 via a universal joint 12, anintermediate shaft 13, and a universal joint 14 in this order.

The steering operation mechanism 15 includes a rack-and-pinionmechanism, for example. The steering operation mechanism 15 turnssteered wheels (not depicted) such as tires in accordance withtransmitted rotation of the steering shaft 3. The steering shaft 3extends in the longitudinal direction of the vehicle body 2.Hereinafter, the direction in which the steering shaft 3 extends iscalled “axial direction X” of the steering shaft 3. The axial directionX is inclined with respect to the horizontal direction so that the otherend 3B is positioned lower than the one end 3A. The rear side that isthe one end 3A side in the axial direction X is denoted by referencecharacter X1, and the front side that is the opposite side from the oneend 3A in the axial direction X is denoted by X2.

Out of orthogonal directions orthogonal to the axial direction X, thedirection perpendicular to the plane of the page in FIG. 1 is called“right-and-left direction Y”, and the direction extending substantiallyvertically in FIG. 1 is called “up-and-down direction Z”. In theright-and-left direction Y, the side farther from a viewer with respectto the plane of the page of FIG. 1 is the right side Y1, and the sidecloser to the viewer with respect to the plane of the page is the leftside Y2. In the up-and-down direction Z, the upper side is denoted byreference character Z1, and the lower side is denoted by Z2. In thedrawings other than FIG. 1, the axial direction, the rear side, thefront side, the right-and-left direction, the right side, the left side,the up-and-down direction, the upper side, and the lower side aredenoted by the same reference characters as in FIG. 1.

The steering shaft 3 includes an upper shaft 20 and a lower shaft 21that extend in the axial direction X. The upper shaft 20 is positionedcloser to the rear side X1 than the lower shaft 21 is, and is disposedconcentrically with the lower shaft 21. A rear end 20A of the uppershaft 20 is the one end 3A of the steering shaft 3. A front end 21A ofthe lower shaft 21 is the other end 3B of the steering shaft 3. A rearend portion 21B of the lower shaft 21 is inserted into a front endportion 20B from the front side X2. The front end portion 20B is formedin the upper shaft 20 so as to have a cylindrical shape.

The lower shaft 21 is coupled to the upper shaft 20 by spline fitting orserration fitting. Thus, the upper shaft 20 and the lower shaft 21 canrotate together and can move relatively to each other along the axialdirection X. By movement of the upper shaft 20 in the axial direction Xwith respect to the lower shaft 21, the steering shaft 3 can contractand extend along the axial direction X.

The column jacket 4 as a whole is a hollow body extending in the axialdirection X. The column jacket 4 accommodates and holds the steeringshaft 3. The column jacket 4 includes an upper jacket 22 and a lowerjacket 23 each having a tubular shape extending in the axial directionX. The upper jacket 22 is positioned closer to the rear side X1 than thelower jacket 23. A front end portion 22A of the upper jacket 22 isinserted into a rear end portion 23A of the lower jacket 23 from therear side X1. The upper jacket 22 in this state can move relatively tothe lower jacket 23 in the axial direction X. By this movement of theupper jacket 22 relative to the lower jacket 23, the entire columnjacket 4 can contract and extend along the axial direction X.

The rear end portion 22B of the upper jacket 22 is coupled to the uppershaft 20 via a bearing 24. The front end portion 23B of the lower jacket23 is coupled to the lower shaft 21 via a bearing 25. Thus, the columnjacket 4 supports the steering shaft 3 via the bearing 24 and thebearing 25 so that the steering shaft 3 is rotatable. The upper shaft 20and the upper jacket 22 that are coupled to each other can moverelatively to the lower shaft 21 and the lower jacket 23 in the axialdirection X. Accordingly, the column jacket 4 can contract and extendtogether with the steering shaft 3. This extension and contraction ofthe steering shaft 3 and the column jacket 4 is called “telescoping”.Adjusting the position of the one end 3A (i.e., the steering member 11coupled to the one end 3A) of the steering shaft 3 in the axialdirection X by the telescoping is called “telescopic adjustment”.

The lower bracket 5 includes a pair of right and left movable brackets5A (see also FIG. 2), a fixed bracket 5B, and a central shaft 5C. Themovable brackets 5A are fixed to an upper-side outer peripheral surfaceof the front end portion 23B of the lower jacket 23. The fixed bracket5B is fixed to the vehicle body 2. The central shaft 5C extends in theright-and-left direction Y. The central shaft 5C is disposed so as toextend between the movable brackets 5A and passes through the fixedbracket 5B. Thus, the front end portion 23B of the lower jacket 23 iscoupled to the vehicle body 2. The movable brackets 5A are formed on thefront end portion 23B of the lower jacket 23. Thus, the central shaft 5Cis disposed in a position closer to the front side X2 in the columnjacket 4.

The movable brackets 5A are supported by the fixed bracket 5B so as tobe pivotable about the central shaft 5C. Thus, the entire column jacket4 together with the steering shaft 3 can pivot about the central shaft5C up and down with respect to the fixed bracket 5B and the upperbracket 6. This pivoting of the column jacket 4 about the central shaft5C serving as a pivot axis is called “tilt”, and the substantiallyvertical direction along a circular arc centered on the central shaft 5Cis called “tilt direction C”. The tilt direction C is an intersectingdirection vertically intersecting the axial direction X, and isorthogonal to the right-and-left direction Y. The up-and-down directionZ, which is an intersecting direction vertically intersecting the axialdirection X and is a tangential direction to the tilt direction C, isorthogonal to the right-and-left direction Y.

Adjusting the position of the steering member 11 in the tilt direction Cby the tilt is called “tilt adjustment”. By causing the column jacket 4to pivot along the tilt direction C, the tilt adjustment can beperformed. The lower jacket 23 is coupled to the vehicle body 2 via thelower bracket 5, and thus cannot move in the axial direction X.Accordingly, during the telescopic adjustment, the upper jacket 22actually moves.

The upper bracket 6 is a bracket that supports the rear end portion 23Aof the lower jacket 23 and via which the rear end portion 23A is coupledto the vehicle body 2. As seen in FIG. 2 that is a perspective view ofthe steering system 1, the upper bracket 6 integrally includes a pair ofside plates 30 and a connecting plate 31 that is thin in the up-and-downdirection Z. The pair of the side plates 30 are thin in theright-and-left direction Y and face each other with the rear end portion23A of the lower jacket 23 interposed therebetween. The connecting plate31 is joined to the respective upper end portions of the pair of theside plates 30.

In the pair of the side plates 30, at the same position when viewed fromthe right-and-left direction Y, tilt slots 32 are formed. The tilt slots32 extend in a circular-arc-like manner along the tilt direction C. Theconnecting plate 31 has portions extending outward of the pair of theside plates 30 in the right-and-left direction Y. The entire upperbracket 6 is fixed to the vehicle body 2 (see FIG. 1) by bolts (notdepicted), for example, that are inserted thereinto.

On the upper-side outer peripheral surface of the lower jacket 23, aslit 33 is formed that extends over the entire area in the axialdirection X and penetrates the lower jacket 23 in the up-and-downdirection Z. On the rear end portion 23A of the lower jacket 23, a pairof extending portions 34 are integrally formed that define the slit 33from the right-and-left direction Y and extend toward the upper side Z1.Each extending portions 34 has a plate-like shape extending in the axialdirection X and the up-and-down direction Z and is thin in theright-and-left direction Y. The pair of the extending portions 34 aredisposed between the pair of the side plates 30. Each extending portion34 faces, from the right-and-left direction Y, the corresponding sideplate 30 that is positioned on the same side in the right-and-leftdirection Y.

FIG. 3 is a sectional view along line III-III in FIG. 1. In FIG. 3, thevirtual plane including the central axis 3C of the steering shaft 3 andextending in the up-and-down direction Z is called “reference plane 3D”.As seen in FIG. 3, at positions in the pair of the extending portions 34that are the same when viewed from the right-and-left direction Y,circular insertion holes 35 are formed that penetrate the respectiveextending portions 34 in the right-and-left direction Y. The insertionholes 35 of the pair of the extending portions 34 overlap part of thetilt slots 32 of the pair of the side plates 30 of the upper bracket 6when viewed from the right-and-left direction Y.

The position adjustment mechanism 7 is a mechanism configured to releaselocking of the position of the steering member 11 (see FIG. 1) for tiltadjustment and telescopic adjustment, and to lock the position of thesteering member 11 after the tilt adjustment and the telescopicadjustment. The position adjustment mechanism 7 includes a tilt bolt 40as a clamping shaft, an operation member 41, a cam 42, a moving member43, a nut 44, a moving member 45, a needle roller bearing 46, and athrust washer 47.

The tilt bolt 40 is a metallic bolt having a central axis 40A extendingin the right-and-left direction Y. The tilt bolt 40 has a head portion40B at the left end portion thereof and a thread groove 40C formed onthe outer peripheral surface at the right end portion thereof. A portionof the tilt bolt 40 extending on the right side Y1 of the head portion40B is inserted into the tilt slots 32 of the pair of the side plates 30and the insertion holes 35 of the pair of the extending portions 34 inpositions closer to the upper side Z1 than the steering shaft 3. In thisstate, the head portion 40B is positioned closer to the left side Y2than the side plate 30 on the left side Y2, and the thread groove 40C ispositioned closer to the right side Y1 than the side plate 30 on theright side Y1.

The operation member 41 is a lever, for example, that can be gripped. Ina base end portion 41A of the operation member 41, an insertion hole 41Bpenetrating the operation member 41 in the right-and-left direction Y isformed. Into the insertion hole 41B, the left end portion of the tiltbolt 40 is inserted, and the base end portion 41A is fixed to the tiltbolt 40. Thus, a user such as a driver can hold a grip 41C of theoperation member 41 on the side opposite from the base end portion 41Ain the longitudinal direction thereof to operate the operation member41. The tilt bolt 40 rotates integrally with the operation member 41about the central axis 40A in accordance with operation of the operationmember 41.

The cam 42 integrally includes an annular plate portion 42A and atubular boss portion 42B. The plate portion 42A is adjacent to the baseend portion 41A of the operation member 41 from the right side Y1. Theboss portion 42B extends from the plate portion 42A toward the left sideY2. Into a space defined by the respective inner peripheral surfaces ofthe plate portion 42A and the boss portion 42B, the tilt bolt 40 isinserted. The boss portion 42B is inserted into the insertion hole 41Bof the operation member 41. The cam 42 rotates integrally with the tiltbolt 40 and the operation member 41.

FIG. 4 is an exploded perspective view of the tilt locking mechanism 9on the left side Y2. In FIG. 4, the moving member 43 is a metallicsintered body, for example. The moving member 43 integrally includes afirst pressing portion 51, a second pressing portion 52, and a bossportion 53. The first pressing portion 51 has a plate-like shape that isthin in the right-and-left direction Y, and is substantially rectangularwhen viewed from the right-and-left direction Y. In the substantialcenter of the first pressing portion 51 when viewed from theright-and-left direction Y, a circular through-hole 51A penetrating thefirst pressing portion 51 in the right-and-left direction Y is formed.The right side surface of the first pressing portion 51 is called “firstpressing surface 54”.

The second pressing portion 52 has a block-like shape protruding fromthe first pressing surface 54 toward the right side Y1, and issubstantially circular when viewed from the right side Y1. On both sidesof the second pressing portion 52 in the up-and-down direction Z, flatsurfaces 52A that are flat along the axial direction X and theright-and-left direction Y are each formed. The right side surface ofthe second pressing portion 52 is called “second pressing surface 55”.The second pressing surface 55 has a substantially semicircular shapeprotruding outward in the axial direction X, and a pair of the secondpressing surfaces 55 are provided so as to be separate from each otherin the axial direction X. The through-hole 51A of the first pressingportion 51 also penetrates, along the right-and-left direction Y, aportion of the second pressing portion 52 between the pair of the secondpressing surfaces 55.

The boss portion 53 has a small piece-like shape protruding from thesecond pressing portion 52 between the pair of the second pressingsurfaces 55 toward the right side Y1, and is substantially rectangularwhen viewed from the right side Y1. End surfaces 53A of the boss portion53 on both sides in the axial direction X are flat along the tiltdirection C, specifically the tangential direction to the tilt directionC. The flat surface 52A of the second pressing portion 52 on the upperside Z1 is flush with the upper end surface of the boss portion 53. Theflat surface 52A of the second pressing portion 52 on the lower side Z2is flush with the lower end surface of the boss portion 53. Hereinafter,the upper end surface and the lower end surface of the boss portion 53are considered to be part of the flat surfaces 52A. The through-hole 51Aof the first pressing portion 51 also penetrates the boss portion 53along the right-and-left direction Y. In the right end surface of theboss portion 53, a notch 53B cutting out the boss portion 53 along theaxial direction X is formed. The notch 53B is formed on both sides ofthe through-hole 51A in the axial direction X, and communicates with thethrough-hole 51A. Thus, the boss portion 53 is divided into upper andlower parts by the through-hole 51A and the notches 53B.

As seen in FIG. 3, into the through-hole 51A of the moving member 43,the left end portion of the tilt bolt 40 is inserted with a smallclearance. The first pressing portion 51 of the moving member 43 isadjacent to the plate portion 42A of the cam 42 from the right side Y1.On the right side surface of the plate portion 42A and the left sidesurface of the first pressing portion 51, cam protrusions 56 are formed.The boss portion 53 of the moving member 43 is inserted into the tiltslot 32 of the side plate 30 on the left side Y2. The respective endsurfaces 53A of the boss portion 53 on both sides in the axial directionX lie along a pair of edge portions 32A extending parallel to each otheralong the tilt direction C in the tilt slot 32 (see FIG. 4). Thisprevents idle rotation of the moving member 43 in the tilt slot 32 andcorotation of the moving member 43 with the tilt bolt 40.

The pair of the second pressing surfaces 55 of the second pressingportion 52 of the moving member 43 are in contact with, from the leftside Y2, peripheral portions of the tilt slot 32 at the left sidesurface of the side plate 30 on the left side Y2. To the thread groove40C of the tilt bolt 40, the nut 44 is attached. Between the nut 44 andthe side plate 30 on the right side Y1, the moving member 45, theannular needle roller bearing 46, and the thrust washer 47 are arrangedin this order from the left side Y2.

The shape of the moving member 45 is substantially the same as the shapeof the moving member 43, as the moving member 43 is flipped to the rightside Y1 with respect to the reference plane 3D. However, unlike themoving member 43, the moving member 45 does not have the cam protrusion56. Portions of the moving member 45 that correspond to the respectiveportions of the moving member 43 are denoted by the same referencecharacters, and detailed description of those portions is omitted. Theright end portion of the tilt bolt 40 is inserted into each of themoving member 45, the needle roller bearing 46, and the thrust washer47. Into the through-hole 51A of the moving member 45, the right endportion of the tilt bolt 40 is inserted with a small clearance. The bossportion 53 of the moving member 45 is inserted into the tilt slot 32 onthe right side Y1. In the same manner as in the moving member 43, idlerotation of the moving member 45 in the tilt slot 32 and corotation ofthe moving member 45 with the tilt bolt 40 are prevented. The secondpressing surfaces 55 of the second pressing portion 52 of the movingmember 45 are in contact with, from the right side Y1, peripheralportions of the tilt slot 32 at the right side surface of the side plate30 on the right side Y1.

In the tilt slots 32 of the right and left side plates 30 in the upperbracket 6, the tilt bolt 40 can move in the tilt direction C along thetilt slots 32 together with the respective boss portions 53 of themoving members 43 and 45. In the insertion holes 35 of the lower jacket23 of the column jacket 4, the tilt bolt 40 can rotate about the centralaxis 40A but cannot move in the other directions. Thus, when the columnjacket 4 is tilted for tilt adjustment, the tilt bolt 40 pivots in thetilt direction C together with the column jacket 4. In this manner, theupper bracket 6 supports the column jacket 4 via the tilt bolt 40 sothat the column jacket 4 is pivotable. Tilt adjustment is performedwithin a movable range of the boss portions 53 in the tilt slots 32.

When the user operates and rotates the operation member 41 aftertelescopic adjustment and/or tilt adjustment, the cam 42 rotates, andthe cam protrusions 56 of the cam 42 and the moving member 43 ride oneach other. This causes the moving member 43 to move toward the rightside Y1 along the tilt bolt 40 extending in the right-and-left directionY, thereby pressing the second pressing surface 55 against the left sidesurface of the side plate 30 on the left side Y2 from the left side Y2.Accordingly, the moving member 45 is pulled along the tilt bolt 40toward the left side Y2, and the second pressing surfaces 55 of themoving member 45 press the right side surface of the side plate 30 onthe right side Y1 from the right side Y1. Thus, the distance between themoving member 43 and the moving member 45 in the right-and-leftdirection Y is narrowed, whereby the pair of the side plates 30 areclamped between the moving member 43 and the moving member 45 from bothsides in the right-and-left direction Y. In this state, each extendingportion 34 is frictionally held by the corresponding side plate 30, andthe upper jacket 22 is frictionally held by the lower jacket 23 that isreduced in diameter by the clamping. This prevents rotation andextension/contraction of the column jacket 4, thereby preventing thesteering member 11 (see FIG. 1) from moving in the tilt direction C andthe axial direction X.

The state of the steering system 1 in which the position of the steeringmember 11 is locked in the tilt direction C and the axial direction X inthis manner is called “locked state”. The respective positions of themoving member 43 and the moving member 45 in the right-and-leftdirection Y in the locked state are called “locked positions”. Duringnormal driving, the steering system 1 is in the locked state. In thesteering system 1 in the locked state, when the operation member 41 isoperated to be rotated toward the direction opposite to that describedabove, the cam 42 rotates relatively to the moving member 43. Thisreleases the riding of the cam protrusions 56 of the cam 42 and themoving member 43 on each other. Accordingly, the moving member 43 movesalong the tilt bolt 40 from the locked position toward the left side Y2.In conjunction with this movement of the moving member 43, the movingmember 45 moves along the tilt bolt 40 toward the right side Y1. Thiswidens the distance between the moving member 43 and the moving member45, thereby releasing the clamping of the pair of the side plates 30between the moving member 43 and the moving member 45. In this state,the frictional holding between each side plate 30 and the correspondingextending portion 34 and the frictional holding between the lower jacket23 and the upper jacket 22 are released. This allows rotation andextension/contraction of the column jacket 4, so that the steeringmember 11 can move in the tilt direction C and the axial direction X.Telescopic adjustment and tilt adjustment are thus enabled again.

The state of the steering system 1 in which the fixing of the positionof the steering member 11 is released in the tilt direction C and theaxial direction X is called “released state”. The respective positionsof the moving member 43 and the moving member 45 in the right-and-leftdirection Y in the released state are called “released positions”. Thetelescopic locking mechanism 8 includes a tubular locking member 57, atransmission member 58, and a locking plate 59. The telescopic lockingmechanism 8 firmly locks the position of the upper jacket 22 in theaxial direction X by intermeshing between teeth 60 on the outerperipheral surface of the locking member 57 and teeth 61 of the lockingplate 59, and releases this intermeshing to release the locking of theupper jacket 22. In the steering system 1 in the locked state, theposition adjustment mechanism 7 locks the position of the upper jacket22 in the axial direction X with frictional force. Intermeshing betweenthe teeth 60 and the teeth 61 further enhances this locking.

The tilt locking mechanism 9 is a mechanism configured to, in thesteering system 1 in the locked state, firmly lock the position of thecolumn jacket 4 in the tilt direction C and release this locking. Thetilt locking mechanism 9 is provided near each of the pair of the sideplates 30. As seen in FIG. 4, the tilt locking mechanism 9 on the leftside Y2 includes the moving member 43, a tooth engagement portion 65, atooth member 66, an elastic member 67, and a spacer 68. The toothengagement portion 65 is provided to the side plate 30 on the left sideY2.

The tooth engagement portion 65 is formed integrally with the side plate30 on the left side Y2 by extrusion molding, for example, and protrudesfrom the left side surface of the side plate 30 on the left side Y2toward the left side Y2. Thus, in FIG. 4, the tooth engagement portion65 is positioned behind the side plate 30 on the left side Y2. On theright side surface of the side plate 30 on the left side Y2, as a markof extrusion molding, a depression 65A the size of which issubstantially the same as that of the tooth engagement portion 65 isformed. The tooth engagement portion 65 is formed in a pair so as tosandwich the tilt slot 32 from both sides in the axial direction X. Thetooth engagement portions 65 each integrally have a holding portion 70and a first tooth row 71. The holding portion 70 extends in a belt-likeshape along the tilt direction C. The first tooth row 71 protrudes fromthe holding portion 70 toward the tilt slot 32. Because the pair of thetooth engagement portions 65 are arranged side by side in the axialdirection X, the first tooth row 71 is formed in a pair arranged side byside in the axial direction X. The pair of the first tooth rows 71include one first tooth row 71A and the other first tooth row 71B. Theone first tooth row 71A is positioned on the front side X2 of the tiltslot 32. The other first tooth row 71B is positioned on the rear side X1of the tilt slot 32. The first tooth row 71A is positioned closer to thecentral shaft 5C (see FIG. 1) of the lower bracket 5 that is a pivotaxis of the column jacket 4, and the first tooth row 71B is positionedmore distant from the central shaft 5C than the first tooth row 71A.

FIG. 5 is a sectional view along line V-V in FIG. 3. As seen in FIG. 5,the left end surfaces of the holding portions 70 are engaged surfaces70A that are flat in the axial direction X and the tilt direction C.Each first tooth row 71 includes a plurality of first teeth 72 that arearranged at regular intervals along the circular-arc-like tilt directionC. Each first tooth 72 is substantially triangular when viewed from theleft side Y2, and has a tooth tip 72A that is directed to the tilt slot32 side. Specifically, the tooth tip 72A of each first tooth 72 in thefirst tooth row 71A on the front side X2 is directed to the rear side X1to face the tilt slot 32. The tooth tip 72A of each first tooth 72 inthe first tooth row 71B on the rear side X1 is directed to the frontside X2 to face the tilt slot 32. In each first tooth 72, a tooth trace72B formed by the corresponding tooth tip 72A extends in theright-and-left direction Y (see also FIG. 8 described later). The leftend surfaces of the first teeth 72 are each flush with the engagedsurface 70A of the holding portion 70.

As seen in FIG. 4, each tooth member 66 is formed by processing onemetal plate by press molding, for example. The tooth member 66integrally includes a body portion 74, a pair of second tooth rows 75, apair of ribs 76, and a pair of spring portions 77. The body portion 74has a plate-like shape that is thin in the right-and-left direction Y,and has a substantially rectangular shape long in the tilt direction C.The right side surface of the body portion 74 is an engaging surface 74Athat is flat in the axial direction X and the tilt direction C.

In the substantial center of the body portion 74 in the axial directionX and the up-and-down direction Z, a through-hole 78 penetrating thebody portion 74 in the right-and-left direction Y is formed. When viewedfrom the right-and-left direction Y, the through-hole 78 has asubstantially circular shape having substantially the same size as thatof the second pressing portion 52 of the moving member 43. Thus, in thebody portion 74, peripheral portions 78A define both ends of thethrough-hole 78 in the up-and-down direction Z. The peripheral portions78A extend parallel to the flat surfaces 52A of the second pressingportion 52.

The second tooth rows 75 are each formed on both end edges of the bodyportion 74 in the axial direction X. Each second tooth row 75 includes aplurality of second teeth 82 that are arranged at regular intervalsalong the tilt direction C. Each second tooth 82 is substantiallytriangular when viewed from the right-and-left direction Y, and has atooth tip 82A that is directed outward of the body portion 74 in theaxial direction X. Specifically, in the second tooth row 75A on thefront side X2 that is formed on the front end edge of the body portion74, out of the pair of the second tooth rows 75, the tooth tip 82A ofeach second tooth 82 is directed to the front side X2. In the secondtooth row 75B on the rear side X1 that is formed on the rear end edge ofthe body portion 74, the tooth tip 82A of each second tooth 82 isdirected to the rear side X1. In each second tooth 82, a tooth trace 82Bformed by the corresponding tooth tip 82A extends in the right-and-leftdirection Y (see also FIG. 8 described later). The left end surface ofeach second tooth 82 is part of the left side surface of the bodyportion 74, and the right end surface of each second tooth 82 is part ofthe engaging surface 74A of the body portion 74.

The pair of the ribs 76 are formed by bending both end portions of thebody portion 74 in the up-and-down direction Z toward the left side Y2.Accordingly, each rib 76 is thin in the up-and-down direction Z, andextends long and narrow along the axial direction X. The pair of thespring portions 77 each have a support portion 83 and a deformationportion 84. The support portion 83 protrudes from each rib 76 so as tobe separated from the body portion 74 in the up-and-down direction Z.The deformation portion 84 is supported by the support portion 83 andcan elastically deform in the right-and-left direction Y. The supportportion 83 of the spring portion 77 on the upper side Z1, out of thepair of the spring portions 77, extends from a rear end portion 76A ofthe rib 76 on the upper side Z1 toward the upper side Z1. The supportportion 83 of the spring portion 77 on the lower side Z2 extends from afront end portion 76B of the rib 76 on the lower side Z2 toward thelower side Z2. Each support portion 83 is a plate-like shape that isthin in the right-and-left direction Y. The deformation portion 84 ofthe spring portion 77 on the upper side Z1 extends from the front endportion of the support portion 83 obliquely toward the front side X2 andthe right side Y1. The deformation portion 84 of the spring portion 77on the lower side Z2 extends from the rear end portion of the supportportion 83 on the lower side Z2 obliquely toward the rear side X1 andthe right side Y1. On a distal end portion of each deformation portion84, a contact portion 84A is formed having a projecting shape pressedout toward the right side Y1.

The tooth member 66 is disposed between the first pressing portion 51 ofthe moving member 43 and the side plate 30 on the left side Y2. As seenin FIG. 6 that is a sectional view along line VI-VI in FIG. 5, into thethrough-hole 78 of the body portion 74 of the tooth member 66, thesecond pressing portion 52 of the moving member 43 is inserted. In thisstate, the tooth member 66 can move relatively to the second pressingportion 52 in the right-and-left direction Y. However, because thethrough-hole 78 has substantially the same size as that of the secondpressing portion 52 as described above, rotation of the tooth member 66relative to the moving member 43 is restricted.

The engaging surface 74A of the body portion 74 in the tooth member 66faces an area, in the left side surface of the side plate 30 on the leftside Y2, between the pair of the first tooth rows 71 (see FIG. 4). Thecontact portions 84A of the spring portions 77 of the tooth member 66are in contact with the left side surface of the side plate 30 on theleft side Y2 from the left side Y2 (see FIG. 5). The elastic member 67is a coned disc spring, for example. In FIG. 6, the elastic member 67has a substantially annular shape that widens in the radial direction ofthe tilt bolt 40 toward the right side Y1. Alternatively, the elasticmember 67 may have a substantially annular shape that widens in theradial direction toward the left side Y2.

Into the hollow portion of the elastic member 67, the second pressingportion 52 of the moving member 43 is inserted. The elastic member 67 isdisposed between the tooth member 66 and the first pressing portion 51of the moving member 43. The inner peripheral edge of the left endportion of the elastic member 67 lies along portions in the outerperipheral surface of the second pressing portion 52 other than the flatsurfaces 52A (see FIG. 4). The right end portion of the elastic member67 is in contact with the left side surface of the body portion 74 ofthe tooth member 66 and part of the second tooth rows 75 (see FIG. 5).

The spacer 68 is a metallic sintered body, for example, having anannular shape that is thin in the right-and-left direction Y (see FIG.4). The spacer 68 is fit onto the second pressing portion 52 of themoving member 43 from the right side Y1. The inner peripheral surface ofthe spacer 68 lies along portions in the outer peripheral surface of thesecond pressing portion 52 other than the flat surfaces 52A (see FIG.5). The spacer 68 is disposed between the first pressing portion 51 ofthe moving member 43 and the elastic member 67. The left side surface ofthe spacer 68 is in surface contact with the first pressing surface 54of the first pressing portion 51 from the right side Y1. The entire areaof the right side surface of the spacer 68 in the circumferentialdirection is in contact with the left end portion of the elastic member67 from the left side Y2.

As described above, the tilt bolt 40 that can pivot together with thecolumn jacket 4 in the tilt direction C is inserted into thethrough-hole 51A of the moving member 43. The second pressing portion 52of the moving member 43 is inserted into the tooth member 66, theelastic member 67, and the spacer 68. Thus, during tilt adjustment, thetooth member 66, the elastic member 67, and the spacer 68 pivot togetherwith the column jacket 4 in the tilt direction C.

As seen in FIG. 3, the tilt locking mechanism 9 on the right side Y1includes the moving member 45 instead of the moving member 43. The tiltlocking mechanism 9 on the right side Y1 includes the tooth engagementportion 65, the tooth member 66, the elastic member 67, and the spacer68 in the same manner as the tilt locking mechanism 9 on the left sideY2. Each of the moving member 45, the tooth engagement portions 65 (notdepicted), the tooth member 66, the elastic member 67, and the spacer 68of the tilt locking mechanism 9 on the right side Y1 and each of themoving member 43, the tooth engagement portions 65, the tooth member 66,the elastic member 67, and the spacer 68 of the tilt locking mechanism 9on the left side Y2 are disposed symmetrically with respect to thereference plane 3D.

The following describes operation of the tilt locking mechanism 9 on theleft side Y2. The operation of the tilt locking mechanism 9 on the rightside Y1 is almost the same as the operation of the tilt lockingmechanism 9 on the left side Y2 except that the right-and-leftorientation is reversed. Operation of the tilt locking mechanism 9 whenthe steering system 1 is changed into the locked state will be describedfirst. In FIG. 5 and FIG. 6, the steering system 1 in the locked stateis illustrated. In the following description, unless otherwisementioned, it is assumed that, in a stage before the steering system 1is changed into the locked state, the first teeth 72 of the first toothrows 71 and the second teeth 82 of the second tooth rows 75 arepositioned so that the phases thereof match each other and thus theseteeth do not overlap each other when viewed from the right-and-leftdirection Y.

When the operation member 41 (see FIG. 3) is operated to change thesteering system 1 into the locked state, the moving member 43 movestoward right side Y1 from the released position to the locked position.The tooth member 66 is caused to move toward the right side Y1 by thefirst pressing portion 51 of the moving member 43 via the spacer 68 andthe elastic member 67. Consequently, when the steering system 1 has beenchanged into the locked state, as depicted in FIG. 5 and FIG. 6, thetooth member 66 reaches the area between the pair of the first toothrows 71 on the left side surface of the side plate 30 on the left sideY2 in the upper bracket 6. Thus, the second tooth rows 75 of the toothmember 66 become close to the first tooth rows 71, and the engagingsurface 74A of the body portion 74 of the tooth member 66 (see FIG. 6)comes into surface contact with the left side surface of the side plate30 on the left side Y2. In this state, the first teeth 72 of the firsttooth row 71A on the front side X2 in the side plate 30 and the secondteeth 82 of the second tooth row 75A on the front side X2 in the toothmember 66 mesh with each other alternately arranged in the tiltdirection C. The first teeth 72 of the first tooth row 7113 on the rearside X1 and the second teeth 82 of the second tooth row 75B on the rearside X1 mesh with each other alternately arranged in the tilt directionC.

Thus, the pair of the first tooth rows 71 and the pair of the secondtooth rows 75 intermesh with each other. Accordingly, in this state, thecolumn jacket 4 that moves integrally with the tooth member 66 cannotpivot, so that the position of the column jacket 4 in the tilt directionC is fixed. Thus, in the locked state, by frictional holding betweeneach extending portion 34 of the lower jacket 23 and the correspondingside plate 30 of the upper bracket 6, and intermeshing between the firsttooth rows 71 and the second tooth rows 75, the position of the upperjacket 22 in the tilt direction C is more firmly locked.

In the locked state, the deformation portions 84 of the spring portions77 of the tooth member 66 are pressed against the side plates 30 toelastically deform in the right-and-left direction Y. Accordingly, byrestoring force of the deformation portions 84 returning to theiroriginal state, the entire tooth member 66 is biased toward the elasticmember 67 on the left side Y2 as depicted in FIG. 6. The elastic member67 is sandwiched by the tooth member 66 and the first pressing portion51 of the moving member 43 to be compressed in the right-and-leftdirection Y, whereby the restoring force returning to the original stateis generated.

It is assumed in FIG. 1 that, in the event of a vehicle collision, aftera primary collision in which a vehicle collides with an obstacle, asecondary collision occurs in which a driver collides with the steeringmember 11. In the secondary collision, by reaction force that isgenerated by deployment of an airbag mounted in the steering member 11and collision of the driver with the airbag, the steering member 11receives an impact in the axial direction X and the tilt direction C. Inthe tilt direction C in particular, the steering member 11 attempts tomove upward together with the column jacket 4. However, in the steeringsystem 1, the position of the column jacket 4 in the axial direction Xand the tilt direction C is maintained by the position adjustmentmechanism 7 and, in addition, the positions of the column jacket 4 andthe steering member 11 in the tilt direction C are firmly maintained bythe tilt locking mechanism 9. Thus, in the secondary collision, freemovement of the column jacket 4 in an initial stage in particular can besuppressed, and the position of the airbag in the tilt direction C canbe maintained properly. When the steering member 11 moves toward thefront side X2 so as to absorb the impact in the secondary collision, thesteering member 11 can be caused to move forward in a stable attitude.This can stabilize detachability in the secondary collision. Maintainingthe position of the column jacket 4 by the tilt locking mechanism 9 asdescribed above is called “positive locking”.

FIG. 7 is a schematic diagram illustrating the first tooth rows 71 andthe second tooth rows 75 that mesh with each other. As seen in FIG. 7,when the column jacket 4 attempts to move upward in the secondarycollision as described above, the tooth member 66 also attempts to moveupward as indicated by the white arrow. Even under normal conditionsother than the secondary collision, for example, when the user exerts astrong upward force on the steering member 11, the column jacket 4 andthe tooth member 66 attempt to move upward.

When the tooth member 66 is about to move upward, each second tooth 82of the second tooth row 75A on the front side X2 in the tooth member 66,at a tooth flank 82C thereof, receives a reaction force F1 from thecorresponding first tooth 72 of the first tooth row 71A on the frontside X2. Each second tooth 82 of the second tooth row 75B on the rearside X1 in the tooth member 66, at a tooth flank 82C thereof, receives areaction force F2 from the corresponding first tooth 72 of the firsttooth row 71B on the rear side X1. The directions of the reaction forcesF1 and F2 are substantially orthogonal to the respective tooth flanks82C. The component force Fx1 of the reaction force F1 in the axialdirection X is directed to the rear side X1, and the component force Fx2of the reaction force F2 in the axial direction X is directed to thefront side X2.

Herein, the tooth tip angle α of each first tooth 72 in the first toothrow 71A on the front side X2 that is closer to the central shaft 5C isdifferent from the tooth tip angle β of each first tooth 72 in the firsttooth row 71B on the rear side X1 that is closer to the steering member11. The tooth tip angles α and β are each an intersecting angle betweeneach pair of tooth flanks 72C that become closer to each other towardthe tooth tip 72A of the first tooth 72. This difference between thetooth tip angle α and the tooth tip angle β causes a difference betweenthe component force Fx1 and the component force Fx2 in the state inwhich the pair of the first tooth rows 71 and the pair of the secondtooth rows 75 intermesh with each other. Accordingly, the tooth member66 is biased in the axial direction X. This reduces backlash between thefirst teeth 72 and the second teeth 82, thereby causing the first teeth72 and the second teeth 82 to firmly mesh with each other. Consequently,meshing strength between the first teeth 72 and the second teeth 82 canbe increased, in other words, strength of the positive locking can beincreased.

When the first teeth 72 are arranged in each of the pair of the firsttooth rows 71 along the tilt direction C, the pitch of the first teeth72 in the first tooth row 71A that is closer to the central shaft 5C issmaller than the pitch of the first teeth 72 in the first tooth row 71Bthat is more distant from the central shaft 5C than the first tooth row71A. In this case, as the pitch of the first teeth 72 decreases, thecontact area between the first teeth 72 and the second teeth 82 thatmesh with each other decreases. Thus, the meshing strength between thefirst teeth 72 of the first tooth row 71A and the second teeth 82 of thesecond tooth row 75A is lower than the meshing strength between thefirst teeth 72 of the first tooth row 71B and the second teeth 82 of thesecond tooth row 75B. Thus, the strength of the positive locking isdetermined by the meshing strength between the first teeth 72 of thefirst tooth row 71A and the second teeth 82 of the second tooth row 75A.However, because of dimensional tolerances, clearance 80 is inevitablygenerated between the first teeth 72 and the second teeth 82 that meshwith each other, and the backlash due to this clearance 80 may reducethe meshing strength. Meanwhile, reduction in the backlash by increasingthe dimensional accuracy of the first teeth 72 and the second teeth 82may increase the cost.

In view of this, the tooth tip angle α of the first teeth 72 in thefirst tooth row 71A is set to be smaller than the tooth tip angle β ofthe first teeth 72 in the first tooth row 71B. For example, when thetooth tip angle α is 60 degrees, the tooth tip angle β is 70 degrees. Bysetting the tooth tip angle α to be smaller than the tooth tip angle β,the component force Fx1 in the axial direction X that the second teeth82 receive from the first teeth 72 of the first tooth row 71A becomessmaller than the component force Fx2 in the axial direction X that thesecond teeth 82 receive from the first teeth 72 of the first tooth row71B. Accordingly, by the difference between the component force Fx1 andthe component force Fx2, the tooth member 66 is biased toward thecentral shaft 5C side (front side X2) in the axial direction X. Thisreduces the backlash between the first teeth 72 of the first tooth row71A and the second teeth 82 of the second tooth row 75A, so that thefirst teeth 72 and the second teeth 82 firmly mesh with each other.Consequently, the contact ratio between the first teeth 72 of the firsttooth row 71A and the second teeth 82 of the second tooth row 75Aincreases, and thus the meshing strength between the first teeth 72 andthe second teeth 82 can be increased.

Without increasing the dimensional accuracy of the first teeth 72 andthe second teeth 82, the meshing strength can be increased by onlysetting the difference between the tooth tip angle α and the tooth tipangle β to reduce the backlash as described above, and thus the cost canbe prevented from increasing. Because the tooth tip angle β is set to belarger than the tooth tip angle α, the contact area between the firstteeth 72 of the first tooth row 71B and the second teeth 82 of thesecond tooth row 75B on the rear side X1 is relatively large. Thus, themeshing strength between the first teeth 72 and the second teeth 82 issufficiently obtained.

The tooth tip angle γ of the second teeth 82 of the second tooth row 75Athat mesh with the first teeth 72 of the first tooth row 71A and thetooth tip angle θ of the second teeth 82 of the second tooth row 75Bthat mesh with the first teeth 72 of the first tooth row 71B may be setto be different as in the relationship between the tooth tip angles αand β. The tooth tip angles γ and θ are each an intersecting anglebetween each pair of tooth flanks 82C that become closer to each othertoward the tooth tip 82A of the corresponding second tooth 82. Asdescribed above, when the tooth tip angle α is set to be smaller thanthe tooth tip angle β, the tooth tip angle γ only needs to be set to besmaller than the tooth tip angle θ. The tooth tip angle α and the toothtip angle γ are preferably equal, and in the same manner, the tooth tipangle β and the tooth tip angle θ are preferably equal.

The following describes operation of the tilt locking mechanism 9 whenthe steering system 1 is changed from the locked state into the releasedstate. The following refers to also FIG. 8 illustrating the releasedstate of the steering system 1 in FIG. 6. When the operation member 41is operated to change the steering system 1 into the released state, themoving member 43 moves from the locked position toward the left side Y2.When the moving member 43 moves toward the left side Y2, the distancebetween the tooth member 66 and the first pressing portion 51 of themoving member 43 increases, and accordingly the compressed amount of theelastic member 67 in the right-and-left direction Y gradually decreases.When the steering system 1 has been changed into the released state asdepicted in FIG. 8, the elastic member 67 becomes uncompressed.

As described above, when the steering system 1 is in the locked state,the deformation portions 84 of the spring portions 77 of the toothmember 66 are elastically deformed. Accordingly, the entire tooth member66 is biased toward the left side Y2 by the restoring force of thedeformation portions 84. When the moving member 43 is moved toward theleft side Y2 and the elastic member 67 accordingly becomes uncompressedto change the steering system 1 into the released state, the toothmember 66 moves toward the left side Y2 by the restoring force of thedeformation portions 84. Accordingly, the second tooth rows 75 of thetooth member 66 also move toward the left side Y2. Thus, when thesteering system 1 has been changed into the released state, the secondtooth rows 75 has moved to be positioned more toward the left side Y2than the first tooth rows 71. This releases the intermeshing between thesecond tooth rows 75 and the first tooth rows 71. The position of themoving member 43 in the right-and-left direction Y at this time iscalled “released position”.

As described above, in the released state, the frictional force betweenthe side plates 30 of the upper bracket 6 and the extending portions 34of the lower jacket 23 disappears. Thus, in the released state, lockingof the position of the column jacket 4 in the tilt direction C iscompletely released. This allows tilt adjustment of the steering member11. FIG. 9 is a diagram illustrating a state in which the second toothrows 75 ride on the first tooth rows 71 in FIG. 5. The following assumesa case in which the user operates the operation member 41 so as tochange the steering system 1 into the locked state, with the secondtooth rows 75 riding on the first tooth rows 71. In the state in whichthe second tooth rows 75 are riding on the first tooth rows 71, asdepicted in FIG. 9, the first teeth 72 and the second teeth 82 overlapeach other when viewed from the right-and-left direction Y due to theunmatched phases. Thus, so-called a tooth-on-tooth position occurs, inwhich the first tooth rows 71 and the second tooth rows 75 do not meshwith each other and the second tooth rows 75 ride on the first toothrows 71. The state of the steering system 1 in which the tooth-on-toothposition occurs is called “tooth-on-tooth state”.

In the tooth-on-tooth state, in the same manner as in the locked state,the position of the column jacket 4 is locked by the position adjustmentmechanism 7 (see FIG. 1). The steering member 11 is locked at theposition where tilt adjustment has been completed. Thus, regardless ofwhether the first tooth rows 71 and the second tooth rows 75 mesh witheach other, tilt adjustment can be performed steplessly within a rangein which the boss portion 53 of the moving member 43 can move in thetilt slot 32.

In the tooth-on-tooth state, the position of the column jacket 4 in thetilt direction C is locked mainly by the frictional force between theside plate 30 and the extending portion 34. Thus, when impact caused bya secondary collision, for example, exceeds the frictional force, thecolumn jacket 4 attempts to pivot in the tilt direction C. In this case,when the column jacket 4 pivots in the tilt direction C by an amountequivalent to about one half of the pitch of the first teeth 72 and thesecond teeth 82, the first teeth 72 of the first tooth rows 71 and thesecond teeth 82 of the second tooth rows 75 are alternately arranged inthe tilt direction C. This prevents the second tooth rows 75 from ridingon the first tooth rows 71. The tooth member 66 having the second toothrows 75 receives the restoring force of the elastic member 67 that iscompressed in the right-and-left direction Y. Thus, the tooth member 66moves toward the side plate 30 of the upper bracket 6, and the firsttooth rows 71 and the second tooth rows 75 mesh with each other. Thus,the steering system 1 is changed from the tooth-on-tooth state into thelocked state. Consequently, by the positive locking, pivoting of thecolumn jacket 4 in the tilt direction C can be prevented.

By the combination of the elastic member 67 using a coned disc springand the spacer 68, the restoring force can be kept substantiallyconstant. This enables the user to operate the operation member 41smoothly without feeling heaviness during the entire operation even withthe second tooth rows 75 riding on the first tooth rows 71. Needless tosay, the elastic member 67 and the spacer 68 may be omitted asnecessary.

The present invention is not limited to the embodiment described above,and various modifications may be made within the scope of the claims.For example, in the embodiment, the first tooth rows 71 are formedintegrally with each side plate 30 of the upper bracket 6 as part of thecorresponding tooth engagement portions 65 so as to be supported by theupper bracket 6. Alternatively, the first tooth rows 71 may be formedseparately from the side plate 30. The tooth member 66 having the secondtooth rows 75 may be formed integrally with the moving member 43 and themoving member 45. Regarding these modifications, the following describesa first modification to a third modification of the tilt lockingmechanisms 9. In the following description, the tilt locking mechanism 9on the left side Y2 will be described. The structure of the tilt lockingmechanism 9 on the right side Y1 is the same as that of the tilt lockingmechanism 9 on the left side Y2.

FIG. 10 is an exploded perspective view of a tilt locking mechanismaccording to the first modification. In FIG. 10 and later-describedFIGS. 11 and 12, members that are the same as the members described inthe foregoing are denoted by the same reference characters, anddescription thereof is omitted. In the first modification, as a memberseparated from a side plate 30, a tooth member 85 is provided. The toothmember 85 is a metal plate that is substantially rectangular when viewedfrom the right-and-left direction Y and is thin in the right-and-leftdirection Y In the substantial center of the tooth member 85 when viewedfrom the right-and-left direction Y, a guide slot 85A penetrating thetooth member 85 in the right-and-left direction Y is formed. The guideslot 85A extends along the tilt direction C. A pair of first tooth rows71 are formed integrally with the tooth member 85 so as to rim bothsides of the guide slot 85A in the axial direction X. In the same manneras in the embodiment, in each first tooth row 71, a plurality of firstteeth 72 are arranged at regular intervals along the tilt direction C.

Tooth tips 72A of the first teeth 72 of the first tooth row 71A on thefront side X2 are exposed to the guide slot 85A toward the rear side X1.Tooth tips 72A of the first teeth 72 of the first tooth row 71B on therear side X1 are exposed to the guide slot 85A toward the front side X2.The first teeth 72 in either row have tooth traces 72B extending alongthe right-and-left direction Y. On both outer sides of the guide slot85A in the axial direction X in the tooth member 85, insertion slots 85Bextending straight along the up-and-down direction Z and penetrating thetooth member 85 in the right-and-left direction Y are each formed.

Insertion slots 30A each having substantially the same shape as that ofeach insertion slot 85B are each formed on both outer sides of the tiltslot 32 in the axial direction X in the side plate 30 on the left sideY2. The insertion slots 30A extend straight along the up-and-downdirection Z and penetrate the side plate 30 on the left side Y2 in theright-and-left direction Y. Along the insertion slots 85B and 30A, apair of long block-like support members 86 are provided. Projectingportions 86A formed on the left side surfaces of the support members 86are inserted into the insertion slots 85B from the right side Y1.Projecting portions 86B formed on the right side surfaces of the supportmembers 86 are inserted into the insertion slots 30A from the left sideY2. Consequently, the tooth member 85 is supported by the side plate 30on the left side Y2 via the support members 86. The tooth member 85 ispositioned separated from the side plate 30 on the left side Y2 towardthe left side Y2, and the guide slot 85A overlap the tilt slot 32 whenviewed from the right-and-left direction Y. The tooth member 85 haselasticity, and thus the first tooth row 71A can elastically deform inthe right-and-left direction Y. The support members 86 may be membersseparated from the side plate 30, or may be formed integrally with theside plate 30.

The tooth member 66 (see FIG. 4) is omitted, and the pair of the secondtooth rows 75 in the tooth member 66 are formed on a moving member 43.Thus, in the first modification, the moving member 43 also serves as thetooth member 66. The second tooth rows 75 in this case are formedintegrally with the moving member 43 on both side surfaces of a secondpressing portion 52 in the axial direction X. In the same manner as inthe embodiment, in each second tooth row 75, a plurality of second teeth82 are arranged at regular intervals along the tilt direction C. Toothtips 82A of the second teeth 82 of the second tooth row 75A on the frontside X2 are directed to the front side X2. Tooth tips 82A of the secondteeth 82 of the second tooth row 75B on the rear side X1 are directed tothe rear side X1. The second teeth 82 in either row have tooth traces82B extending along the right-and-left direction Y.

This tilt locking mechanism 9 of the first modification may be differentin detail from the tilt locking mechanism 9 of the embodiment. Forexample, in the tilt locking mechanism 9 of the first modification, theboss portion 53 of the moving member 43 is formed in a cylindricalshape, and is inserted into the guide slot 85A of the tooth member 85and the tilt slot 32 of the side plate 30. The elastic member 67 is acoil spring that is fitted onto the boss portion 53 and the tilt bolt40, and is inserted into the guide slot 85A and the tilt slot 32. Theelastic member 67 is compressed between the second pressing portion 52of the moving member 43 and the extending portion 34 on the left side Y2in the lower jacket 23 (see FIG. 3), thereby generating a restoringforce described above. In the first modification, the spacer 68 may beomitted.

In the first modification, when the operation member 41 is operated tochange the steering system 1 into the locked state, the moving member 43moves toward the right side Y1 from the released position to the lockedposition. When the steering system 1 has been changed into the lockedstate, the second pressing portion 52 of the moving member 43 that hasreached the locked position reaches the inside of the guide slot 85A ofthe tooth member 85, that is, an area between the pair of the firsttooth rows 71. In this state, the first teeth 72 of the first tooth row71A on the front side X2 and the second teeth 82 of the second tooth row75A on the front side X2 in the moving member 43 mesh with each otheralternately arranged in the tilt direction C. The first teeth 72 of thefirst tooth row 71B on the rear side X1 and the second teeth 82 of thesecond tooth row 75B on the rear side X1 mesh with each otheralternately arranged in the tilt direction C. In this manner, the pairof the first tooth rows 71 and the pair of the second tooth rows 75intermesh with each other.

When the operation member 41 is operated in the opposite direction tochange the steering system 1 from the locked state into the releasedstate, the moving member 43 moves from the locked position toward theleft side Y2 and reaches the released position. At this time, by therestoring force of the elastic member 67, movement of the moving member43 to the released position is facilitated. When the steering system 1has been changed into the released state, the second tooth rows 75 movetoward the left side Y2 relatively to the first tooth row 71, so thatthe intermeshing between the second tooth rows 75 and the first toothrows 71 is released.

When the operation member 41 is operated to change the steering system 1into the locked state with the second tooth rows 75 riding on the firsttooth rows 71, the first tooth rows 71 is pressed by the second toothrows 75. This causes the first tooth rows 71 to elastically deformtoward the side plate 30 on the left side Y2. Thus, the steering system1 is changed into the tooth-on-tooth state. In the first modificationalso, the tooth tip angle α of each first tooth 72 in the first toothrow 71A on the front side X2 in the pair of the first tooth rows 71 isdifferent from the tooth tip angle β of each first tooth 72 in the firsttooth row 71B on the rear side X1. The tooth tip angle α is preferablyset to be smaller than the tooth tip angle β. Accordingly, in asecondary collision, for example, the moving member 43 is biased towardthe front side X2, which reduces backlash between the first teeth 72 ofthe first tooth row 71A and the second teeth 82 of the second tooth row75A. Thus, the meshing strength between the first teeth 72 and thesecond teeth 82 can be increased as described above.

FIG. 11 is an exploded perspective view of a tilt locking mechanism 9according to the second modification. The tilt locking mechanism 9according to the second modification is different in detail from thetilt locking mechanism 9 according to the first modification.Specifically, in the tilt locking mechanism 9 according to the secondmodification, a pair of first tooth rows 71 are not positioned so as torim a guide slot 85A, but are formed integrally with a tooth member 85on its both side edges in the axial direction X. In each first tooth row71, a plurality of first teeth 72 are arranged at regular intervalsalong the tilt direction C. Tooth tips 72A of the first teeth 72 of thefirst tooth row 71A on the front side X2 are directed to the front sideX2. Tooth tips 72A of the first teeth 72 of the first tooth row 71B onthe rear side X1 are directed to the rear side X1. The first teeth 72 ineither row have tooth traces 72B extending along the right-and-leftdirection Y.

In the second modification, both end portions of a first pressingportion 51 of a moving member 43 in the axial direction X are, as bentportions 51B, bent toward the right side Y1. The bent portions 51B areformed in a pair and face each other in the axial direction X. In themoving member 43, second tooth rows 75 are not formed on opposite sidesurfaces of a second pressing portion 52 in the axial direction X, butare integrally formed on the respective facing surfaces of the pair ofthe bent portions 51B. In each second tooth row 75, a plurality ofsecond teeth 82 are arranged at regular intervals along the tiltdirection C. Tooth tips 82A of the second teeth 82 of the second toothrow 75A on the front side X2 are directed to the rear side X1. Toothtips 82A of the second teeth 82 of the second tooth row 75B on the rearside X1 are directed to the front side X2. The second teeth 82 in eitherrow have tooth traces 72B extending along the right-and-left directionY.

In the second modification, when the operation member 41 is operated tochange the steering system 1 into the locked state, the moving member 43moves toward the right side Y1 from the released position to the lockedposition. When the steering system 1 has been changed into the lockedstate, the second pressing portion 52 of the moving member 43 that hasreached the locked position reaches the inside of the guide slot 85A ofthe tooth member 85, and the pair of the bent portions 51B of the firstpressing portion 51 of the moving member 43 catch the tooth member 85from both sides in the axial direction X. In this state, the first teeth72 of the first tooth row 71A on the front side X2 in the tooth member85 and the second teeth 82 of the second tooth row 75A on the front sideX2 in the moving member 43 mesh with each other alternately arranged inthe tilt direction C. The first teeth 72 of the first tooth row 71B onthe rear side X1 and the second teeth 82 of the second tooth row 75B onthe rear side X1 mesh with each other alternately arranged in the tiltdirection C. Thus, the pair of the first tooth rows 71 and the pair ofthe second tooth rows 75 intermesh with each other.

When the operation member 41 is operated in the opposite direction tochange the steering system 1 from the locked state into the releasedstate, in the same manner as in the first modification, the intermeshingbetween the second tooth rows 75 and the first tooth rows 71 isreleased. In the second modification also, in the same manner as in thefirst modification, the steering system 1 can be in the tooth-on-toothstate. In the second modification also, the tooth tip angle α of eachfirst tooth 72 in the first tooth row 71A on the front side X2 isdifferent from the tooth tip angle β of each first tooth 72 in the firsttooth row 71B on the rear side X1. The tooth tip angle α is preferablyset to be smaller than the tooth tip angle β. It should be noted that,in the second modification, the front-and-rear positional relationshipbetween the first tooth rows 71 and the second tooth rows 75 that meshwith each other is the reverse of that in the embodiment and the firstmodification. Thus, in a secondary collision, for example, the componentforce Fx1 (see FIG. 7) is directed to the front side X2, and thecomponent force Fx2 (see FIG. 7) is directed to the rear side X1. Whenthe tooth tip angle α is smaller than the tooth tip angle β, thecomponent force Fx1 is smaller than the component force Fx2, and thusthe moving member 43 is biased toward the rear side X1 in the secondmodification. Even in this case, backlash between the first teeth 72 ofthe first tooth row 71A and the second teeth 82 of the second tooth row75A is reduced. Thus, the meshing strength between the first teeth 72and the second teeth 82 can be increased as described above.

FIG. 12 is an exploded perspective view of a tilt locking mechanism 9according to the third modification. In the third modification, a tiltslot 32 of a side plate 30 of the upper bracket 6 is wide in the axialdirection X, and extends straight along the tangential direction to thetilt direction C, that is, the up-and-down direction Z. Thus, duringtilt adjustment, the tilt bolt 40 can move on a circular-arc-liketrajectory along the tilt direction C within the straight tilt slot 32.

In the third modification, as members separated from the side plate 30,a first tooth member 88 and a second tooth member 89 are provided. Thefirst tooth member 88 is a metal plate that is substantially rectangularwhen viewed from the right-and-left direction Y and is thin in theright-and-left direction Y. In the substantial center of the first toothmember 88 when viewed from the right-and-left direction Y, a guide slot88A penetrating the first tooth member 88 in the right-and-leftdirection Y is formed. The guide slot 88A extends straight along theup-and-down direction Z. The guide slot 88A is narrower than the tiltslot 32 in the axial direction X. Into the guide slot 88A, the tilt bolt40 is inserted.

In the left side surface of the side plate 30 on the left side Y2, onboth outer sides of the tilt slot 32 in the up-and-down direction Z,rib-like guide portions 90 that protrude toward the left side Y2 andextend straight along the axial direction X are integrally formed. Thefirst tooth member 88 is disposed between the upper and lower guideportions 90, and is supported by the side plate 30 via these guideportions 90. The first tooth member 88 can slide in the axial directionX along the guide portions 90, but cannot move in directions other thanthe axial direction X. In the left side surface of the side plate 30 onthe left side Y2, on both outer sides of the tilt slot 32 in the axialdirection X, reception grooves 91 that are recessed toward the rightside Y1 and extend parallel to the tilt slot 32 are each formed.

A pair of first tooth rows 71 are formed integrally with the first toothmember 88 on its both side edges in the axial direction X. Unlike theembodiment, the first modification, and the second modification, aplurality of first teeth 72 are arranged straight at regular intervalsalong the up-and-down direction Z in each first tooth row 71 in thethird modification. Tooth tips 72A of the first teeth 72 of the firsttooth row 71A on the front side X2 are directed to the front side X2.Tooth tips 72A of the first teeth 72 of the first tooth row 71B on therear side X1 are directed to the rear side X1. The first teeth 72 ineither row have tooth traces 72B extending along the right-and-leftdirection Y.

The second tooth member 89 is formed in a block-like shape that is longin the axial direction X and is thin in the right-and-left direction Y,and is disposed closer to the left side Y2 than the first tooth member88. In the substantial center of the second tooth member 89 in the axialdirection X, a fitting hole 89A penetrating the second tooth member 89in the right-and-left direction Y is formed. The fitting hole 89Acorresponds to a second pressing portion 52 of a moving member 43 whenviewed from the right-and-left direction Y, and the second pressingportion 52 is fitted into the fitting hole 89A from the left side Y2.Accordingly, the second tooth member 89 is integrated into the movingmember 43.

Both end portions of the second tooth member 89 in the axial direction Xare, as bent portions 89B, bent toward the right side Y1. The bentportions 89B are formed in a pair and face each other in the axialdirection X. Second tooth rows 75 are integrally formed on therespective facing surfaces of the pair of the bent portions 89B. Toothtips 82A of the second teeth 82 of the second tooth row 75A on the frontside X2 are directed to the rear side X1, and tooth tips 82A of thesecond teeth 82 of the second tooth row 75B on the rear side X1 aredirected to the front side X2. The second teeth 82 in either row havetooth traces 82B extending along the right-and-left direction Y. In eachsecond tooth row 75 in the third modification, the second teeth 82 arearranged straight at regular intervals along the up-and-down direction Zin the same manner as in the first tooth row 71.

The tilt locking mechanism 9 of the third modification may be furtherdifferent in detail from the tilt locking mechanism 9 of the embodiment.For example, in the tilt locking mechanism 9 of the third modification,the second pressing portion 52 of the moving member 43 has asubstantially rectangular profile when viewed from the right side Y1. Aboss portion 53 of the moving member 43 is formed in a cylindricalshape. The second pressing portion 52 is fitted into the guide slot 88Aof the first tooth member 88. In this state, the moving member 43 canslide along the up-and-down direction Z, but cannot move in the otherdirections.

An elastic member 67 is a leaf spring that is substantially rectangularwhen viewed from the right-and-left direction Y, and curves so as tobulge toward the left side Y2. In the center of the elastic member 67when viewed from the right-and-left direction Y, a fitting hole 67A thatis substantially rectangular is formed. On four corners of thesubstantially rectangular elastic member 67, claw-like engagementportions 67B bending and extending toward the left side Y2 are eachintegrally formed. The engagement portions 67B engage with the secondtooth member 89. Accordingly, the elastic member 67 is positioned on thesecond tooth member 89, and the second pressing portion 52 is fittedinto the fitting hole 67A. Accordingly, the elastic member 67 ispositioned on the moving member 43. The elastic member 67 is compressedbetween the first tooth member 88 and the second tooth member 89. Thisgenerates the restoring force. In the third modification, the spacer 68may be omitted.

In the third modification, when the operation member 41 is operated tochange the steering system 1 into the locked state, the moving member 43moves together with the second tooth member 89 toward the right side Y1from the released position to the locked position. When the movingmember 43 has reached the locked position to change the steering system1 into the locked state, the pair of the bent portions 89B of the secondtooth member 89 catch the first tooth member 88 from both sides in theaxial direction X. In this state, the first teeth 72 of the first toothrow 71A on the front side X2 in the first tooth member 88 and the secondteeth 82 of the second tooth row 75A on the front side X2 in the secondtooth member 89 mesh with each other alternately arranged in theup-and-down direction Z. The first teeth 72 of the first tooth row 71Bon the rear side X1 and the second teeth 82 of the second tooth row 75Bon the rear side X1 mesh with each other alternately arranged in theup-and-down direction Z. Thus, the pair of the first tooth rows 71 andthe pair of the second tooth rows 75 intermesh with each other.

When the operation member 41 is operated in the opposite direction tochange the steering system 1 from the locked state into the releasedstate, the moving member 43 moves together with the second tooth member89 from the locked position toward the left side Y2 and reaches thereleased position. At this time, by the restoring force of the elasticmember 67, movement of the moving member 43 and the second tooth member89 to the released position is facilitated. When the steering system 1has been changed into the released state, the second tooth rows 75 havemoved to be positioned more toward the left side Y2 than the first toothrow 71. This releases the intermeshing between the second tooth rows 75and the first tooth rows 71. In this state, when the column jacket 4 istilted, the second tooth member 89 pivots on the circular-arc-liketrajectory along the tilt direction C together with the tilt bolt 40. Atthis time, the second tooth member 89 moves relatively to the firsttooth member 88 in the up-and-down direction Z, and moves integrallytherewith in the axial direction X. Thus, the first tooth rows 71 arealways disposed at the same positions as those of the correspondingsecond tooth rows 75 in the axial direction X. Consequently, even if thefirst tooth rows 71 and the second tooth rows 75 do not extend in acircular-arc-like manner along the tilt direction C but extend straightalong the up-and-down direction Z unlike the embodiment, the firstmodification, and the second modification, the first tooth rows 71 andthe second tooth rows 75 can reliably mesh with each other after tiltadjustment.

When the operation member 41 is operated to change the steering system 1into the locked state with the second tooth rows 75 riding on the firsttooth rows 71, the first tooth rows 71 elastically deform toward theside plate 30 on the left side Y2 and are received by the receptiongrooves 91 of the side plate 30 on the left side Y2. Thus, the steeringsystem 1 is changed into the tooth-on-tooth state. In the thirdmodification also, the tooth tip angle α of each first tooth 72 in thefirst tooth row 71A on the front side X2 is different from the tooth tipangle β of each first tooth 72 in the first tooth row 71B on the rearside X1. The tooth tip angle α is preferably set to be smaller than thetooth tip angle β. In a secondary collision, for example, in the samemanner as the moving member 43 of the second modification, the secondtooth member 89 is biased toward the rear side X1. This reduces backlashbetween the first teeth 72 of the first tooth row 71A and the secondteeth 82 of the second tooth row 75A. Consequently, as described above,the meshing strength between the first teeth 72 and the second teeth 82can be increased.

The present invention can be applied not only to the embodiment and thefirst modification to the third modification, but also to any tiltlocking mechanism 9 in which tooth traces 72B of first teeth 72 andtooth traces 82B of second teeth 82 extend along the right-and-leftdirection Y parallel to the central axis 40A of a tilt bolt 40. Thus,the present invention can be applied also to the teeth of the holdingunit and the tooth plate in the steering column described in US2009/0013817 A1. A plurality of second teeth 82 are arranged along thetilt direction C, for example, to constitute a pair of second tooth rows75, but the tooth rows do not have to be constituted. At least onesecond tooth 82 needs to be formed in each of two locations spaced apartfrom each other in the axial direction X, which can mesh with a pair offirst tooth rows 71.

The tilt locking mechanism 9 may be provided on either one of the rightside Y1 and the left side Y2 of the upper bracket 6. The tilt lockingmechanism 9 can also be applied to a steering system that does not havethe telescopic locking mechanism 8, and to a steering system in whichtelescopic adjustment cannot be performed. The tilt locking mechanism 9can also be applied to a steering system 1 in which the connecting plate31 (see FIG. 2) of the upper bracket 6 and the vehicle body 2 (seeFIG. 1) are coupled together by capsules (not depicted). In a secondarycollision, resin pins (not depicted) that are inserted through both ofthe capsules and the connecting plate 31 are broken. This causes theupper bracket 6 to be detached from the vehicle body 2.

The lower jacket 23 only needs to hold the upper jacket 22 as beingclamped by a pair of side plates 30 to be reduced in diameter. Forexample, the end of the slit 33 (see FIG. 2) on the front side X2 may beclosed. The steering system 1 may have, instead of the lower jacket 23,a structure of holding the upper jacket 22 without being reduced indiameter. The steering system 1 is not limited to a manual-type steeringsystem that does not assist steering operation of the steering member11, and may be a column-assist-type electric power steering system thatassists steering operation of the steering member 11 with an electricmotor.

What is claimed is:
 1. A steering system comprising: a steering shaft,to one end of which a steering member is coupled; a column jacket thatholds the steering shaft and is pivotable about a pivot axis that is onthe opposite side of the steering shaft from the one end in an axialdirection; a bracket that is fixed to a vehicle body and supports thecolumn jacket so that the column jacket is pivotable; an operationmember that is operated to allow and prevent pivoting of the columnjacket with respect to the bracket; a pair of tooth rows each includinga plurality of first teeth each of which has a tooth trace extending inan orthogonal direction orthogonal to both of the axial direction and anintersecting direction vertically intersecting the axial direction andthat are arranged along the intersecting direction, the pair of toothrows being supported by the bracket and being arranged side by side inthe axial direction; and a tooth member including a second tooth thathas a tooth trace extending in the orthogonal direction, is formed atleast one in each of two locations spaced apart from each other in theaxial direction, and is configured to mesh with the pair of tooth rows,the tooth member being pivotable together with the column jacket andbeing movable in the orthogonal direction in accordance with operationof the operation member, wherein a tooth tip angle of the first teeth inone tooth row of the pair of tooth rows is different from a tooth tipangle of the first teeth in the other tooth row that is more distantfrom the pivot axis than the one tooth row.
 2. The steering systemaccording to claim 1, wherein the tooth tip angle of the first teeth inthe one tooth row is smaller than the tooth tip angle of the first teethin the other tooth row.